As a support for a printing plate material, a plate of metals such as aluminum has been used. In recent years, a printing plate material employing a plastic sheet support such as a polyester film sheet has been developed in that it is easy to handle or carry (see for example, Japanese Patent O.P.I. Publication Nos. 5-257287, 2000-258899 and 2002-79773).
However, the printing plate employing the plastic sheet support has problem in that when it is mounted on a plate cylinder of a printing press, distortion due to its elongation occurs. As a method to solve this problem, a method is known which intervenes an underlay sheet between the printing plate material and the plate cylinder (see for example, Japanese Patent O.P.I. Publication No. 10-193828).
However, these techniques have still problem that during printing, a printing plate moves on a plate cylinder of a printing press, resulting in variation of length of printed matter, i.e., printing position stability deteriorates. Further, they have another problem that printing properties such as initial ink receptivity and printing durability are greatly lowered. Particularly, this problem is likely to occur after long length storage of the printing plate.